The present invention relates to a method for minimizing cell aging of a battery and, respectively, to a battery comprising an apparatus for minimizing cell aging of the battery.
Motor vehicles comprising an electric drive (electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles etc.) often have so-called electrochemical cells, such as lithium-ion cells or iron-metal hydride cells for example, as storage means for energetic electrical charge. These cells are not in a stable equilibrium state in the state range in which they are used as energy stores. That is to say, firstly the cells discharge with a current which typically lies in the μA or mA range. Secondly, the cells also undergo irreversible decomposition reactions. Therefore, the structures react to a changed chemical composition which limits the range of use of the cell. Therefore, these reactions are called cell aging. Cell aging depends on many factors, so-called aging or acceleration factors. These factors include, as the most important factor, the temperature, but also the state of charge (SOC) of the cell. These two factors are critical determinants of calendar aging, that is to say that aging which is independent of the use of the battery or of the cell. Use-dependent aging factors (so-called cyclical aging) are, for example, the flowing charging and discharging currents, the charging/discharging stroke and also the temperature and further factors. Cell aging can be expressed, for example, with respect to the usable capacitance C, that is to say at the time t0, the capacitance C(t0)=C0. At later times, C(t>t0)<C0 due to aging.
Aging can be described in the form of a model (abstractly) as an aging factor—and state-dependent function:C(t)=f(AF1,AF2,Z1,Z2, . . . ,C0,t).
Here, AF1, AF2 etc. . . . are the abovementioned aging factors. Z1, Z2 etc. describe states, such as storage, charging, discharging etc., and t is time.
An analogous description can also be specified for aging of the internal resistance of the cell or other relevant properties for which the cell has been designed.